Los Boquerones have been one of the competition's surprise packages this season having pipped Serie A giants AC Milan to top spot in Group C.

But the 31-year-old is anticipating a rigorous test of their Champions League credentials in Portugal next week.

"They’ll be very tough opponents. I was fortunate enough to play in Portugal for three years and I really know what they’re about, how competitive they are," he told Fifa.com

"It’ll be a very tricky tie and we’ll have to be very focused right from the first whistle, and not make any mistakes.

"Let’s hope we can put in great performances like we did against Milan and Zenit and play the same way."

The former Barca forward then reflected on the emergence of Lionel Messi as the world's best player and recalled some of his earliest memories of the Argentine.

He added: "When we used to watch him in training he’d astonish us all with the things he could do: the speed he’d get his shots off, the pace he could run with the ball, how humble he was and the fact he had so much quality.

"But none of us imagined he’d come so far in such a short space of time. And there’s so much left! He’s so young and he’s already won the Ballon d’Or four times."